Fuel systems typically employ multiple fuel injectors to inject high pressure fuel into combustion chambers of an engine. This high pressure fuel is supplied to the fuel injectors via a common rail secured to the engine and individual fuel lines connected between the common rail and the fuel injectors. Because of the geometry of the engine and/or other components associated with the engine, the fuel lines typically include bends, and must be fabricated from a thin-walled material that can withstand bending experienced during fabrication without rupture. Although suitable for many applications, such a fuel system configuration may not be suitable for higher pressure applications. Specifically, the strength of the material used to connect the common rail and the fuel injector is a limiting factor in the maximum operating pressure of those fuel systems.
In some configurations, a high strength component is used to form a portion of the conduit between the common rail and the fuel injector, with the remaining portion of the fuel conduit being made up of conventional fuel lines. Such a fuel system is described in U.S. Pat. No. 5,775,303 (the '303 patent) issued to Sweetland et al. on Jul. 7, 1998. The '303 patent describes a high pressure fuel line connection assembly including a fuel line, a fuel injector, and an elongated fuel line adapter conducting fuel from the fuel line to the fuel injector. The fuel line adapter is inserted in an angled bore within the cylinder head and received on one end by a detent formed in an outer portion of the injection nozzle in a region of the injection nozzle for receiving high pressure fuel for injection. A tube nut, positioned about the fuel line, is threadingly engaged with the cylinder head such that the fuel line assembly is in a secured position and such that a compressive force couples the leading end of the fuel line with the second end of the fuel line adapter.
Although the fuel system of the '303 patent may provide a high strength component for a portion of the conduit from the fuel rail to the fuel injector, the operating pressure of fuel systems containing such an arrangement may still be limited by the strength of the fuel line component found in the remainder of the fuel conduit. Furthermore, the configuration described in the '303 patent requires a single connection between the fuel line and the fuel line adapter. Specifically, the single connection between the fuel line and the fuel line adapter may provide a site for leakage to occur.